Manufacture of metal strip suitable for turbine blades



. 24 1929- c. A. PARSONS ET AL 1,729,009

MANUFACTURE OF METAL STRIP SUITABLE FOR TURBINE BLADES Filed Jan. 21, 1928 4 hi hi Fig.2.

Patented Sept. 24, 1929 UNITED STATES PATENT;- OFFICE" cmms nonanon rmsons m Ewan eamr'r nnowrmow, or NEWCASTLE- on-mn, ENGLAND; sun BBOWNLOW ASBIGNOB 'ro. sun rnsons HANUFAQIURE OI .KE'IAL BT31? 'SUITA BLE FOB TURBINE BLADES I Application filed January 81, 1988, Serial No. 848,428, and in Great Britain February 7, 1927.

- The invention relates to the manufacture of metal strip by an extension process such as rolling and is specially applicable to the rolling of metal strip for tur me blades.

In the particular case of reaction turbine blades formed integral with their roots by a rolling process, the blank or billet has a rootforming portion approximating to the final form and a tail portion to be extended and shaped byrolling to form the strip-like projection constituting the blade proper. If as 1s usual the blade-forming portion of the billet is formed for convenience of rectan ular or other simple section, it is found that t e blade curves to one side during the rolling process owing to the greater extension of that part of the billet which forms the thinner edge.

When strip is rolled in long lengths no particular difiiculty is found in providing guides to keep it straight, but in short lengths and particularly as above where each blade is integral with its root such guiding is practically out of the uestion.

The main object of t e present invention is to overcome such diflicultles.

The invention consists in the process of manufacturing metal bar as hereinafter described and particularly set forth in the claims.

Referring to the accompanying drawings, which illustrate diagrammatically one form of the invention Fi re 1 shows in full lines a turbine-blade bla or billet suitable fora cylindrical rotor and having a curved blade-forming, portion, the finished blade being indicated by dotted lines,

Figure 2 being a section on the line 2-2 of Figure 1; while Figure 3 shows a modified form of blank suitable for a conical rotor.

In carrying the invention into efiect according to the form shown as applied by way of example to the production of reaction turbine blading, the blank or billet (see Fi res 1 and 2) has a rectangular root-forming ase,

a, of uniform thickness and a blade-forming tail, 6, of rectangular cross section projecting from a side of the base and of the same 59 thickness as the base. The blade-form g ortion, b, of the blank instead of coinciding 1 in direction with the finished blade is curved as a whole (see the full lines in Figure 1) to that side on which the thinner edge, 12', of the finished blade will be formed.

If the initial curvature ofthe blank is properly chosen the extra extension of that side of the blade-forming ortion which corresponds to the thinner e ge', b, of the finished blade will cause the blank to become less curved during each rolling operation and finally to become straight, as shown by the dotted lines in Figure 1.

The blank as described above with a rec tangular base is suitable for cylindrical rotors or stators but the root-forming portion may be modified, for example as shown ata',

gitudinal extension of one side of the symmetrical blank more than the other side thereof. That is, the curved blank of rectangular cross-section, when subjected to gap-rolling, will straighten out due to the extension of the concave side of the curved blank more than the convex side, the concave side being rolled'thinner than the convex side. I

This variation in lon 'tudinal extension from one side of the bla to the other being gradual is termed differential extension as defining the variation in extension by 'in- Y crements from one side to the other.

Having now described our invention, what. we claim as new and desire to secure by Letters Patent is v ,1. A process of manufacturing metal bar of non-symmetrical cross section, which conextended longitudinall owing sists in preparing a curved billet and reducing the curvature of said billet by differentially extending said billet longitudinally to give the non-symmetrical cross section required, the concave side of said curved billet being extended more than the convex side.

2. A process as claimed in claim 1,' in which the cross section of the curved billet is initially uniform.

3. A rocess of manufacturing turbine blading aving a non-symmetrical cross section with a thicker and a thinner edge, which consists in preparin a billet curved towards that side of the illet which will correspond to said thinner edge of the finished blade and reducing the curvature of said billet by differential y extending said billet longitudinally to give the non-symmetrical cross section required, the concave side of said curved billet being extended more than the convex side.

4. A process of manufacturing turbine blading having a non-symmetrical cross section with a thicker and a thinner edge and an integral base, which consists in preparin a billet having a base-forming portion an a blade-forming portion integral with said base-formin portion and curved towards that side 0 the billet which will correspond to said thinner edge of the finished blade and reducing the curvature of said blade-forming portion of the billet by differentially extending said blade-forming portion only of said billet longitudinally to give the non-symmetrical cross section required, the concave side of said curved billet being extended more than the convex side.

In testimony whereof we havesigned our names to this specification.

CHARLES ALGERNON PARSONS.

EDVARD GARRETT BROWNLOW. 

